What was found
JUST AFTER DEPARTURE THE CREW RECEIVED A "SMOKE TOILET" WARNING MESSAGE. THE PASSENGERS AND F/A COULD SEE AND SMELL SMOKE IN THE LAVATORY AREA. WHEN CB`S WERE PULLED AND THE LAVATORY DOOR OPENED THE SMOKE AND ODOR DISSIPATED. THE ACFT RETURNED UNEVENTFULLY. AFTER EXTENSIVE MX TROUBLESHOOTING THE FAULT WAS TRACED TO THE LAVATORY EXHAUST FAN WHICH HAD FAILED. THE EXHAUST FAN WAS REPLACED AND THE ACFT RETURNED TO SERVICE. EXHAUST FAN, PN AE0405A01.